Abstract Among men who have sex with men (MSM), there is a resurgent epidemic of methamphetamine (meth) and other stimulant use that fuels new HIV infections and compromises the benefits of HIV treatment as prevention. Although MSM living with HIV who use meth can achieve viral suppression, prior research from our team and others has documented that recent stimulant use amplifies immune dysregulation in treated HIV infection. MSM living with HIV are also more likely to report amplified behavioral risk such as condomless anal intercourse that increases risk for HIV acquisition and onward HIV transmission. The scientific premise of this administrative supplement is that co-occurring meth and HIV will create a double jeopardy for the novel coronavirus (COVID-19) pandemic. In order to examine the potentially synergistic effects of meth and HIV for the COVID-19 pandemic, we will enroll 200 MSM in a seroprevalence study testing for IgM and IgG antibodies to the novel coronavirus (SARS-CoV-2). Using an intact groups design, participants will be enrolled based on meth use (user versus non-user) by HIV status (positive versus negative). Among men living with HIV, only those who report an undetectable viral load will be enrolled. Among men who are HIV-negative, only those who are not currently taking pre-exposure prophylaxis (PrEP) will be enrolled. There will be 50 participants enrolled per group: METH+HIV+, METH+HIV-, METH-HIV+, and METH-HIV-. The primary hypothesis is that those with co-occurring meth use and HIV (METH+HIV+) will display the greatest seroprevalence of SARS-CoV-2 relative to meth or HIV alone (METH+HIV- or METH-HIV+) or controls (METH-HIV-). We will also examine the extent to which co-occurring meth and HIV are indirectly linked to higher SARS-CoV-2 seroprevalence via alterations in gut-immune dysregulation, smoking behaviors, and decreased adherence to social distancing guidelines. This supplement will provide some of the first data regarding whether and how those with co- occurring meth use and HIV are more vulnerable to SARS-CoV-2 infection. This represents a crucial first step to identifying high priority populations that will directly inform the development bio-behavioral interventions to mitigate risk for COVID-19. These findings will also inform targeted public health efforts to ?flatten the curve? of community-level SARS-CoV-2 transmission in this rapidly evolving COVID-19 pandemic.